*9395074405* UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certifi cate of Education Advanced Subsidiary Level and Advanced Level CHEMISTRY 9701/23 Paper 2 Structured Questions AS Core May/June 2013 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Data Booklet READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fl uid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. A Data Booklet is provided. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. 1 2 3 4 5 Total This document consists of 11 printed pages and 1 blank page. IB13 06_9701_23/5RP R [Turn over
2 Answer all the questions in the spaces provided. 1 Carbon disulfi de, CS 2, is a volatile, fl ammable liquid which is produced in small quantities in volcanoes. (a) The sequence of atoms in the CS 2 molecule is sulfur to carbon to sulfur. (i) Draw a dot-and-cross diagram of the carbon disulfi de molecule. Show outer electrons only. (ii) Suggest the shape of the molecule and state the bond angle. shape... bond angle... [3] (b) Carbon disulfi de is readily combusted to give CO 2 and SO 2. (i) Construct a balanced equation for the complete combustion of CS 2. (ii) Defi ne the term standard enthalpy change of combustion,. [3]
3 (c) Calculate the standard enthalpy change of formation of CS 2 from the following data. Include a sign in your answer. standard enthalpy change of combustion of CS 2 = 1110 kj mol 1 standard enthalpy change of formation of CO 2 = 395 kj mol 1 standard enthalpy change of formation of SO 2 = 298 kj mol 1 [3] (d) Carbon disulfi de reacts with nitrogen monoxide, NO, in a 1:2 molar ratio. A yellow solid and two colourless gases are produced. (i) Construct a balanced equation for the reaction. (ii) What is the change in the oxidation number of sulfur in this reaction? from... to... [3] [Total: 12] [Turn over
4 2 Methanol, CH 3 OH, can be produced industrially by reacting carbon monoxide, CO, with hydrogen, H 2. CO(g) + 2H 2 (g) CH 3 OH(g) H = 91 kj mol 1 The process is carried out at 4 10 3 kpa (40 atmospheres) and 1150 K. (a) (i) State Le Chatelier's Principle.... [2] (ii) From your understanding of Le Chatelier s Principle, state the conditions of temperature and pressure that could be used in order to produce an increased yield of methanol in this process. In each case, explain why the yield would increase. temperature... explanation... pressure... explanation... [4]
5 (b) The carbon monoxide for use in the production of methanol may be formed by reacting carbon dioxide with hydrogen. CO 2 (g) + H 2 (g) CO(g) + H 2 O(g) K c = 1.44 at 1200 K A mixture containing 0.70 mol of CO 2, 0.70 mol of H 2, 0.30 mol of CO and 0.30 mol of H 2 O was placed in a 1 dm 3 fl ask and allowed to come to equilibrium at 1200 K. Calculate the amount, in moles, of each substance present in the equilibrium mixture at 1200 K. CO 2 + H 2 CO + H 2 O initial 0.70 0.70 0.30 0.30 moles [4] [Total: 10] [Turn over
6 3 This question refers to the elements in the section of the Periodic Table shown below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca... transition elements... Ga Ge As Se Br Kr (a) From this list of elements, identify in each case one element that has the property described. Give the symbol of the element. (i) An element that has molecules which consist of single atoms. (ii) An element that has a molecule which contains exactly four atoms. (iii) The element that is a liquid at room temperature and pressure. (iv) The element in Period 3 (Na to Ar) that has the largest atomic radius. (v) The element in Period 3 (Na to Ar) that has the highest melting point. (vi) The element in Period 3 (Na to Ar) that forms the largest anion. (vii) An element that reacts with water to give a solution that can behave as an oxidising agent. [7]
7 (b) The formulae and melting points of some of the oxides of the elements in Period 3, Na to Cl, are given in the table. formula of oxide Na 2 O MgO Al 2 O 3 SiO 2 P 4 O 6 SO 2 Cl 2 O 7 m.p. / C 1132 2830 2054 1710 24 73 92 (i) Give the formulae of two of these oxides that have simple molecular structures.... and... (ii) Give the formula of one of these oxides that will give no reaction with water when placed in it for a long time.... (iii) Give the formula of the product formed when MgO is reacted with SO 2.... [4] (c) The melting points of the elements Si to Cl are given in the table. element Si P S Cl m.p. / C 1414 44 115 102 (i) Explain why the melting point of Si is very much greater than those of the other three elements. (ii) Suggest why the melting points of the other three elements are in the order S > P > Cl. [4] [Total: 15] [Turn over
8 4 Compound Q, heptan-2-one, is found in some blue cheeses. CH 3 (CH 2 ) 4 COCH 3 compound Q (a) Compound Q may be reduced to R. Compound R may be dehydrated to give two different products, S and T. (i) In the boxes below, draw the structural formulae of R, S, and T. CH 3 (CH 2 ) 4 COCH 3 reduce R dehydrate S T (ii) State the reagents that would be used for each of these reactions in a school or college laboratory. reduction... dehydration... [5]
9 (b) In the boxes below, write the structural formula of the organic compound formed when Q is reacted separately with each reagent under suitable conditions. If you think no reaction occurs, write 'NO REACTION' in the box. Tollens reagent HCN K 2 Cr 2 O 7 / H + [3] (c) The fi rst stage of cheese making is to produce 2-hydroxypropanoic acid (lactic acid) from milk. CH 3 CH(OH)CO 2 H lactic acid Other than the use of a ph indicator, what reagent could you use to confi rm the presence of some lactic acid in a sample of heptan-2-one? State what observation you would make. reagent... observation... [2] [Total: 10] [Turn over
10 5 Compounds containing the allyl group, CH 2 =CHCH 2, have pungent smells and are found in onions and garlic. Allyl alcohol, CH 2 =CHCH 2 OH, is a colourless liquid which is soluble in water. (a) Allyl alcohol behaves as a primary alcohol and as an alkene. Give the structural formula of the organic compound formed when allyl alcohol is reacted separately with each of the following reagents. (i) acidifi ed potassium dichromate(vi), heating under refl ux (ii) bromine in an inert organic solvent (iii) cold, dilute, acidifi ed potassium manganate(vii) (iv) hot, concentrated, acidifi ed potassium manganate(vii) [5] (b) Allyl alcohol undergoes the following reactions. (i) When reacted with concentrated HCl at 100 C, CH 2 =CHCH 2 Cl is formed. State as fully as you can what type of reaction this is. (ii) When reacted with MnO 2 at room temperature, CH 2 =CHCHO is formed. What type of reaction is this? [2]
11 (c) Allyl alcohol can be converted into propanal in two steps. step I step II CH 2 =CHCH 2 OH CH 3 CH 2 CH 2 OH CH 3 CH 2 CHO (i) What reagents and conditions would be used for each step? step I reagent(s)... condition(s)... step II reagent(s)... condition(s)... (ii) Allyl alcohol and propanal are isomers. What form of isomerism do they display? [5] (d) Allyl alcohol may also be converted into propanal by using a ruthenium(iv) catalyst in water. CH 2 =CHCH 2 OH ruthenium(iv) catalyst CH 3 CH 2 CHO Suggest what is unusual about this single step reaction..... [1] [Total: 13] [Turn over
12 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.